For the backend, you
need something with a standard library. Static typing and performance is nice, but if you have to pick-and-match every single little detail where you have to interact with the outside world, you'll still end up with more bugs, just outside of your own code.
So the "P"s of the "LAMP" stack of olden days might be a good first choice, probably switching out Ruby for Perl (as much as that pains me to say -- modern Perl + Mojolicious is awesome, but if you don't know this yet, it's probably too late).
Or C# / Java / Kotlin, if you've already got developers in this space or are willing to pay more and able to adjust to more mature management styles.
Go is somewhere between those two, and so is my current somewhat-happy place (old, but in a non-enterprisey org).
Node and Erlang/Elixir currently are good for some end points, i.e. if you really need a chat module. For the whole backend, I've got my doubts.
For the frontend, as others have said, if it's "just" a website, pick a good template system if you need to and just enhance it with some small javascript if needed (fancy selects and pickers). VanillaJS if you've got good JS programmers, jQuery if you just need fancy modules, (p)react if you need it on your resume.
If you either need to go SPA or need an REST API for other consumers anyway, writing the frontend in the devil's own language, 2015 edition might be necessary. I'm showing my biases again by suggesting something that already made a few choices, or you're bikeshedding again. One reason why React seems to be immensely popular with trainers/coaches. Just buy their 13-part video course and use their personal npms.
Sadly ember seems to be going the way of the dodo, ExtJS is proprietary and paleolithic and Angular strikes me as having a serious case of Java envy (which might be good. If you already picked that or C# for the backend and Struts ain't enough...).
The happy medium in this space seems to be Vue.
For the backend, use Postgres. Model your data properly, before you get to the shiny parts.
I'm not really happy with most of these parts, but that's webdev for you. The last time I enjoyed web programming was with Smalltalk/Seaside, but there's no going back...
For me, right now its:
- Postgres
- Go
- Vue (considering Nuxt)
But for simpler/side projects, I'd seriously look at:
- SQlite
- PHP or Python/Flask
- preact/htm for enhanced widgets
(And I would probably do the latter if I hadn't done Catalyst while everyone else was learning RoR)